[Jays76bird]

Hi everyone got a chance to pick up a set of #16 heads with the screwed in studs and 2.11 intake valves for a reasonable price. Was thinking about using them on the 1974 350 I'm building for my 76 Formula. I read some of Polyakr older post and the bores will have to be chamfered on the intake side. A good head choice ? Or overkill for the 350 ? I was going to take .060 over if I don't have core shifting.

[Jay S]

Nothing wrong with small chambered big valve heads on a 350. Lots of 350s ran a 2.11 intake, late 70s 350s ran 6x-4s. It is a good idea to chamfer the bore for the intake with a mild cam. With a large high lift cam it is mandatory or the intake will hit. I wouldn’t bore the engine more than you have too.

[Will]

Once the machine work is done on the block, bolt the heads on and put a lightweight checking spring on an intake valve and see how much lift you can get before you contact the block.

[steve25]

My recent flow bench test of last fall show ( moving a head around on a Bore adapter) that your better off even with the Bore size of a .060" over 350 motor to either run only a 1.96" Intake valve, or a 2.11" valve with limited lift if your running a pre 1970 head casting.

The deeper chambers of the post 1970 heads will not cut into the added flow numbers of running a 2.11" valve at a lift of up to .450" if I recall my numbers right.

If your 350 build needs to drop some compression then adding the needed Intake valve chamfer to the top of each Bore is a good help!

[hgiv]

Those are highly sought after heads for a 400 build!

I agree that small valve heads with smaller chambers on a 350 are the way to go. Think #46,#17,#47,#15 or "baby 16s" But there a many ways to go depending on what your goal is. Have you cc'd them? But as said with the right cam choice the bigger valves won't hurt you. A ton of guys have done it and your large overbore will help, assuming your block will support it. You don't see that many that go .060 over.

I think you will be fine. Way better better than anything that came on the original motor or after that's for sure!!

[Will]

The factory put #48 heads on the 350 HO, though only with. 407" lift.

[steve25]

These days I wonder if the Engineers really approved of that for the 350 HO motors, as I am sure they new of the shrouding issue.

I think it may have been conceived by the sales people ( great to advertise that the Ho motor came with RA 400 heads!) and given the blessing / go ahead by the Bean counters since it removed assembled unused #48 heads from the parts shelves and sold more cars!

[hgiv]

Originally Posted by Will

The factory put #48 heads on the 350 HO, though only with. 407" lift.

Yeah and built a ton of compression with those #48 heads. Advertised over 10. So they were supposed to be something like 68 cc. Those #16 heads are the same valve size but probably 75cc? We aren't talking about an HO equivalent head. Maybe shave them down a tad. But I would leave them alone.

They are a solid choice for a 350 build. Way better than many options. Not the best. But that's ok cause that wasn't the goal. Just don't over cam it and you'll be happy.

[Half-Inch Stud]

Sounds like a 1968 350 HO combo with 16s, Which sounds like the 1969 350HO with 48s.

Probably a thousand such Head swaps occurred in the 1980s. What i know now is the Steel-reinforced Slugs in those engines convinced me to buy all-aluminum forgings.

And yet, my brother's Convertible remains a 350 2bbl with the small vlave heads and 2-speed auto.

Sooooo, if the 350 is running fine, let it lay. huh. Them 16s could go on a Spare 400 engine.

[Jays76bird]

I ended up purchasing the heads, they had already been modified for valve stem seals,they of course have the screw in studs, aftermarket retainers and locks. definitely need to be cleaned up, I paid $220.00 After looking at the going prices on marketplace and epay I didn't think it was a bad deal. I will clean them up and cc them.

[PunchT37]

Use em. Just do as Will states above. Check valve to bore clearance before buying a higher lift cam. The shrouding that Steve states is real but, on that thing, the compression gain will do more good than the "harm" that the shrouding will.


We ran 061`s on a 68 350 back in the day with a 3 something duration Crane cam. 390 gears. Back then, that car won it`s share of street races. `68 LeMans, N50/15 tires with a 2800 stall. Car did have a fiberglass front cap.

[Jays76bird]

Originally Posted by Half-Inch Stud

Sounds like a 1968 350 HO combo with 16s, Which sounds like the 1969 350HO with 48s.

Probably a thousand such Head swaps occurred in the 1980s. What i know now is the Steel-reinforced Slugs in those engines convinced me to buy all-aluminum forgings.

And yet, my brother's Convertible remains a 350 2bbl with the small vlave heads and 2-speed auto.

Sooooo, if the 350 is running fine, let it lay. huh. Them 16s could go on a Spare 400 engine.

This engine came with the car which was a roller. its not running but on my stand. Most 400's in driving distance are running from $500 to $1600 for a rebuild able motor depending on condition. So I had the 350 so I'm going with that,plus I have seen the 350 Pontiac run well. My cousin Buddy ran a 350 in a LeMans in the late 80s in oval pure stock racing and did quite well with it.

[steve25]

I forget, do the # 48 castings have the RA4 chamber like the 68 1/2 RAII # 96 castings?

['ol Pinion head]

Originally Posted by steve25

I forget, do the # 48 castings have the RA4 chamber like the 68 1/2 RAII # 96 castings?

No, slightly different open chamber.

['ol Pinion head]

The other thing to think about when installing '67-70 big valve (or converted early small valve heads) on 71+ Pontiac V8's is the earlier heads don't have the top accessory bolt hole, the one for the long alternator bolt on '71+ 10SI (37-63 amp) ALT/PS setups. Have detailed before how several times I've taken the entire common style '71+ Alt brackets & loaded PS setup, & trimmed down by a few the threads, the threads on the long alt bolt, then flipped that bolt around backwards. End up using a plastic insert style locking nut at the front pivot hole where the end of the long alt bolt comes through. Little cumbersome to do by yourself in a car (use the cherry picker & a thin fabric ratchet strap if you don't have help), but the flipped bolt trick works well for solving this issue.

[MarkS57]

# 16 heads on 350- did this on an original 68 350 2bbl. In combination with a #67 cam, TH400, Qjet, and duals- nice running engine.

[77 TRASHCAN]

OK, experts. Are the cylinder notches on a 70 350 in the correst place to use #48 heads on the 70 350 block???
Thanks.
LOL, I have these parts, had never thought about that particular combo, before...

[Jay S]

Originally Posted by 77 TRASHCAN

OK, experts. Are the cylinder notches on a 70 350 in the correst place to use #48 heads on the 70 350 block???
Thanks.
LOL, I have these parts, had never thought about that particular combo, before...

I am certainly not a 350 expert. If I remember correct the 70 and 71 350 have chamfer’s on both sides of the bore. Not sure on the 72. 73-75 had none? And a 76-77 that ran the 6x-4 has exhaust bore chamfers only? Not sure what the 68-69 had, guessing both.

FWIW, The bore chamfers on the 70-71 are pretty big and needs a small chamber head to get the compression up to anything respectable. We built a 71 350 with big valve heads and a roller cam to run in a dirt track car. It ran good but the bore chamfers dropped the compression more than we wanted.

[Will]

Originally Posted by steve25

These days I wonder if the Engineers really approved of that for the 350 HO motors, as I am sure they new of the shrouding issue.

I think it may have been conceived by the sales people ( great to advertise that the Ho motor came with RA 400 heads!) and given the blessing / go ahead by the Bean counters since it removed assembled unused #48 heads from the parts shelves and sold more cars!

Would shrouding have been an issue @ .407" lift?

[Will]

Originally Posted by 'ol Pinion head

The other thing to think about when installing '67-70 big valve (or converted early small valve heads) on 71+ Pontiac V8's is the earlier heads don't have the top accessory bolt hole, the one for the long alternator bolt on '71+ 10SI (37-63 amp) ALT/PS setups. Have detailed before how several times I've taken the entire common style '71+ Alt brackets & loaded PS setup, & trimmed down by a few the threads, the threads on the long alt bolt, then flipped that bolt around backwards. End up using a plastic insert style locking nut at the front pivot hole where the end of the long alt bolt comes through. Little cumbersome to do by yourself in a car (use the cherry picker & a thin fabric ratchet strap if you don't have help), but the flipped bolt trick works well for solving this issue.

That's a good solution! Welding a nut to the back of the alternator bracket has also been proposed. That's the route I went, worked fine.